This invention relates to drying systems for web material such as tissue, pulp and paper and using an adjustable deckel in the drying process.
In web drying processes it is very important to maintain a uniform edge moisture profile in the cross machine direction and in the machine direction on papermaking drying machines such as paper, pulp and tissue machines, in order to achieve high quality paper production.
Uneven moisture edge profiles can result in overheating of cylinder edges causing over-dried edges of the web, uneven creping on tissue machines, excessive local wear of tissue cylinders, reduced machine production and increase in raw material consumption.
There are several profiling devices on the market, but none of those provide the profiling requirements need in today""s industry. The following United States patents provide several examples:
U.S. Pat. No. 4,312,139 discloses a material web dryer having opening and closing elements for controlling discharge between open, partially closed, or completely closed positions;
U.S. Pat. No. 3,962,799 discloses a moisture profiler for contacting a moving web, having a pair of sliding valves overlying the inlets from ducts to adjust the hot to warm air ratio;
U.S. Pat. No. 4,331,150 discloses a steam shower for reducing paper web moisture content in a cross machine direction by varying it""s bottom steam discharge area incrementally across the web;
U.S. Pat. No. 4,192,080 discloses a method for improving the drying characteristics of a cylinder drying section of a paper machine having an even transverse moisture profile;
U.S. Pat. No. 4,545,857 discloses a steam box for controlling the moisture content of a paper web, which delivers steam to a series of damper controlled compartments that extend across the web;
U.S. Pat. No. 3,930,319 discloses an apparatus for drying a travelling paper web, having a hot air delivery system adjacent the cylinder, with at least a part of the hot air delivery structure being transversely movable; and
U.S. Pat. No. 3,263,344 discloses a drying system for a papermaking machine having sleeves that allow transverse movement so that the air discharge can be controlled.
The present invention addresses the problem of edge sheet uniformity in the drying section of paper, pulp and especially on tissue drying apparatus. It also addresses the problems associated with hot air spillage caused by dryer air boundary layer and balancing of the process air drying equipment.
According to a broad aspect the invention relates to an adjustable deckel profiler for use in an apparatus for drying a moving web of tissue, pulp or paper, said profiler comprising a slidable member for controlling and adjusting hot process impingement air onto said web and which operatively increases or decreases the process air impinging on said web, and means for adjusting and setting said profiler relative to cross-machine drying air profiling.